High power, solid-state laser gain amplifiers can require high performance cooling to dissipate waste heat fluxes over 100 W/cm2, while maintaining a low temperature rise between a laser gain medium and a coolant. Typically, this high performance cooling is achieved by flowing coolant directly over the gain medium or by attaching to the gain medium a heat sink with internal passages for flowing coolant. However, direct liquid cooling generally requires very high coolant flow rates and pressure drops to cool large heat fluxes. In addition, heat sinks are fabricated from high thermal conductivity materials that may not be well-matched in coefficient of thermal expansion (CTE) to the laser gain medium, which can result in major performance issues, or from CTE-matched material, which is difficult to fabricate microchannel geometry and apply uniformly over large surface areas and results in poorer thermal performance than non-CTE-matched heat sinks. Finally, the use of a liquid metal or a solid material as a thermal interface between the gain medium and a non-CTE-matched heat sink has been considered. However, most of such liquid metals are toxic and/or corrosive, and solid materials have a relatively low thermal conductance, convert fluorescent energy into additional waste heat at the gain medium interface, provide unacceptable uniformity across the gain medium, and can generate stress due to CTE mismatch with the gain medium.